The present invention relates to golf balls and more particularly to golf balls having a soft core.
The spin rate and xe2x80x9cfeelxe2x80x9d of a golf ball are particularly important aspects to consider when selecting a golf ball for play. A golf ball with the capacity to obtain a high rate of spin allows a skilled golfer the opportunity to maximize control over the ball. This is particularly beneficial when hitting a shot on an approach to the green.
Golfers have traditionally judged the softness of a ball by the sound of the ball as it is hit with a club. Soft golf balls tend to have a low frequency sound when struck with a club. This sound is associated with a soft feel and thus is desirable to a skilled golfer.
Balata covered wound golf balls are known for their soft feel and high spin rate potential. However, balata covered balls suffer from the drawback of low durability. Even in normal use the balata covering can become cut and scuffed, making the ball unsuitable for further play. Furthermore, the coefficient of restitution of wound balls is reduced by low temperatures.
The problems associated with balata covered balls have resulted in the widespread use of durable ionomeric resins as golf ball covers. However, balls made with ionomer resin covers typically have PGA compression ratings in the range of 90-100. Those familiar with golf ball technology and manufacture will recognize that golf balls with PGA compression ratings in this range are considered to be somewhat harder conventional balata covered balls. It would be useful to develop a golf ball having a durable cover which has the sound and feel of a balata covered wound ball.
An object of the invention is to provide a golf ball having a soft feel.
Another object of the invention is to provide a golf ball which will travel a long distance when hit.
A further object of the invention is to provide a golf ball which produces a pleasing, soft sound on impact with a golf club.
A further object of the invention is to provide a golf ball having a combination of soft feel and good travel distance.
Another object of the invention is to provide a golf ball with a cover that is more cut resistant and temperature resistant than balata covers.
A final object of the invention is to provide a method for making a golf ball of the type described herein.
Other objects, features, advantages and characteristics of the invention will be in part obvious and in part pointed out more in detail hereinafter.
The invention in a preferred form is a golf ball comprising a solid core having a PGA compression of 55 or less and an outer cover layer having a Shore D hardness of at least 58, the ball having a PGA compression of 80 or less.
In a particularly preferred form of the invention, the outer cover layer has a Shore D hardness of at least 63. The ball preferably has a PGA compression of 70 or less. In a particularly preferred form of the invention, the diameter of the ball is no more than 1.70 inches.
The ball preferably has a high coefficient restitution of at least 0.780, and more preferably at least 0.790.
The golf ball of the present invention has a soft feel which can be defined as a mechanical impedance with a primary minimum value in the frequency range of 3100 Hertz (Hz) or less after the ball has been maintained at 21.1xc2x0 C., 1 atm. and about 50% relative humidity for at least 15 hours. Preferably, the mechanical impedance has a primary minimum value in the frequency range of 100 -3100 Hz and more preferably 1800-3100 Hz after the ball has been maintained at 21.1xc2x0 C., 1 atm. and about 50% relative humidity for at least 15 hours. Even more preferably, the ball has a mechanical impedance with a primary minimum value in the frequency range of 1800-2600 Hz after the ball has been maintained at 21.1xc2x0 C., 1 atm. and about 50% relative humidity for at least 15 hours.
In a preferred form of the invention, the outer cover layer comprises ionomer. Preferably, the outer cover layer contains at least 50 weight % ionomer, and even more preferably at least 70 weight % ionomer. The outer cover layer most preferably contains at least 50 weight % of an ionomeric resin which is formed from an acid copolymer with a melt index of 30 g/10 mins or less prior to neutralization with metal ions, and more preferably 23 g/10 mins or less prior to neutralization (ASTM-D 1238E at 190 Deg. C).
Another preferred form of the invention is a golf ball comprising a solid core and an outer cover layer having a Shore D hardness of at least 58, the ball having a mechanical impedance with a primary minimum value in the frequency range of 3100 Hz or less after the ball has been maintained at 21.1xc2x0 C., 1 atm. and about 50% relative humidity for at least 15 hours. In a particularly preferred form of the invention, the core has a PGA compression of 55 or less. The ball preferably has a PGA compression of 80 or less, and preferably has a mechanical impedance with a primary minimum value in the frequency range of 1800-3100 Hz and more preferably 1800-2600 after the ball has been maintained at 21.1xc2x0 C., 1 atm. and about 50% relative humidity for at least 15 hours.
Yet another preferred form of the invention is a golf ball comprising a solid core having a PGA compression of 55 or less, and an outer cover layer with a Shore D hardness of at least 58, the ball having a mechanical impedance with a primary minimum value in the frequency range of 3100 Hz or less after the ball has been maintained at 21.1xc2x0 C., 1 atm. and about 50% relative humidity for at least 15 hours. The ball preferably has a PGA compression of 80 or less. The outer cover layer preferably has a Shore D hardness of at least 60 and more preferably at least 65. In a particularly preferred form of the invention, the ball has a coefficient of restitution of at least 0.780. The ball preferably has a mechanical impedance with a primary minimum value in the frequency range of 1800-3100 Hz and more preferably 1800-2600 Hz after the ball has been maintained at 21.1xc2x0 C., 1 atm. and about 50% relative humidity for at least 15 hours.
A further preferred form of the invention is a golf ball comprising a core, and an outer cover layer having a Shore D hardness of at least 58, the ball having a mechanical impedance with a primary minimum value in the frequency range of 2600 Hz or less and more preferably 100-2600 Hz after the ball has been maintained at 21.1xc2x0 C., 1 atm. and about 50% relative humidity for at least 15 hours. In a particularly preferred form of the invention, the core has a PGA compression of 55 or less. The ball preferably has a PGA compression of 80 or less.
Yet another preferred form of the invention is a golf ball comprising a core having a PGA compression of 55 or less, and an outer cover layer with a Shore D hardness of at least 58, the ball having a mechanical impedance with a primary minimum value in the frequency range of 2600 Hz or less and more preferably 100-2600 Hz after the ball has been maintained at 21.xc2x0 C., 1 atm. and about 50% relative humidity for at least 15 hours. The ball preferably has a PGA compression of 80 or less. The outer cover layer preferably has a Shore D hardness of at least 60. In a particularly preferred form of the invention, the ball has a coefficient of restitution of at least 0.790.
The invention accordingly comprises the article possessing the features, properties, and the relation of elements exemplified in the following detailed disclosure.